Stock Position Size Calculator
Find how many shares or units fit a fixed budget, or how many you can buy while risking only a set percentage of your account.
Stock Position Size Calculator
Position Size (units)
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Position Value
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% of Account
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Maximum Loss at Stop
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Risk-Reward
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Position relative to account
Assumptions & method
- Fixed-amount mode: units = budget ÷ entry price. Position value = units × entry price.
- Risk-based mode: risk amount = account size × risk % ÷ 100; risk per unit = entry − stop-loss; units = risk amount ÷ risk per unit. Maximum loss = units × risk per unit.
- Long positions only: the stop-loss must be below the entry price and any target above it. Risk-reward = (target − entry) ÷ (entry − stop-loss).
- If the risk-based size would cost more than the account, units are capped at account size ÷ entry price and the cap is flagged. Leverage and margin are not modelled.
- Whole-unit mode rounds units down; fractional mode keeps the exact amount.
- Slippage, gaps through the stop, brokerage, taxes and currency effects are not modelled, so a real loss can exceed the figure shown.
Results are estimates based on the figures you enter. They are not guarantees and not financial advice.
What is position sizing?
Position sizing decides how much to put into one trade or holding before you place it. A fixed-amount approach starts from what you want to invest and divides by the price. A risk-based approach starts from what you are willing to lose: you pick a percentage of your account, mark a stop-loss level, and the distance between entry and stop tells you how many units that loss budget buys. A wider stop means a smaller position for the same risk. Looking at position value as a share of the account shows concentration, while the risk-reward ratio compares the possible gain at your target with the planned loss. Treat the result as arithmetic on your assumptions, since a real exit price can differ from the stop you set.